Seal for a fluid assembly

ABSTRACT

A fluid assembly comprising a first part ( 28 ) and a second part ( 30 ) which interact by relative linear movement therebetween. A groove ( 40 ) extends around the circumference of the cylindrical interacting surface ( 36 ) of the first part ( 38 ) and a seal ( 50 ) is situated within the groove ( 40 ). The seal ( 50 ) has a radial face ( 64 ) which converts from a concave profile to a flat profile flush with the groove&#39;s root side ( 54 ) upon interface with the interacting surface ( 38 ) of the second part ( 30 ). The seal ( 50 ) also has axial faces ( 62 ) which each assume a more pronounced concave profile upon such interfacing, the concave profiles forming cavities ( 68 ) which, when filled with fluid, urge the radial seal face ( 64 ) and radial seal face ( 66 ) towards the groove&#39;s root side ( 54 ) and the interacting surface ( 38 ) of the second part ( 30 ).

RELATED APPLICATION

This application claims priority under 35 U.S.C. §119 (e) to U.S.Provisional Patent Application No. 60/793,146 filed on Apr. 19, 2006.The entire disclosure of this provisional application is herebyincorporated by reference.

GENERAL FIELD

A seal for a fluid assembly comprising linearly interacting parts,wherein the seal is positioned within a groove in the cylindricalinteracting surface of one of the parts.

BACKGROUND

In an offshore drilling operation, a drillstring extends from the rigplatform into a wellbore whereat it drills deeper and deeper into thesea floor. The drillstring extends through a riser which reaches fromthe rig platform to the wellhead, usually with a subsea blowoutprevention (BOP) stack between it and the ocean floor. During drilling,mud removed from the wellbore is drained to the surface through theriser, and well production fluid is transferred to the rig through chokelines. To stop a well flow, high density mud can be pumped from rigtanks into the wellbore by kill lines which extend from the platform tothe seafloor.

The riser may be as long as several thousand feet, and may be made ofsuccessive riser pipes whose adjacent ends are connected/disconnected onthe rig to raise/lower the riser. The choke lines, the kill lines,and/or other auxiliary lines (e.g., pneumatic/hydraulicequipment-control lines and/or logging lines) can be similarly made of aseries of conduits connected/disconnected along with the riser pipes.

The connection between successive choke/kill conduits can beaccomplished by male/female coupling members which interact by relativelinear movement therebetween whereby a radially inner surface of thefemale member interfaces with a radially outer surface of the malemember. To seal the male/female interface, a seal is typically placed ina groove in the radially inner interfacing surface of the femalecoupling member. The role played by choke and kill lines results in thembeing subjected to high pressures, both internal and external, andcontinuous exposure to seawater. To add insult to injury, choke and killlines must endure long term cyclic fatigue loading (tension,compression, bending) which rise/fall in various load combinationsdepending upon the riser-mounting-relationship, sea conditions,production rates and other influencing factors. Needless to say, a sealresiding in a choke line or a kill line does not live a sheltered life.

SUMMARY

A seal is provided, which can be constructed to withstand the abuseimposed by life in a choke line or a kill line in an offshore drillingoperation, while still providing effective (if not superior) sealingperformance. The seal provides multiple sealing points, most if not allof these points constituting exceptionally large bearing areas, evenagainst groove sides and/or corners, thereby allowing the bridging ofsurface imperfections in deteriorated grooves. Opposing axial fluidcavities in the seal urge radial surfaces outward/inward to furtherenergize the seal. While this seal will be especially appreciated in theconnection of choke/kill lines, it will be equally welcomed in otherfluid assemblies where a seal must tolerate high pressures, hightemperatures, load cycling, frequent reciprocating movement, and/orother abusive conditions.

These and other features of the fluid assembly and/or the seal are fullydescribed and particularly pointed out in the claims. The followingdescription and annexed drawings set forth in detail certainillustrative embodiments, these embodiments being indicative of but afew of the various ways in which the principles of the invention may beemployed.

DRAWINGS

FIG. 1 is a schematic diagram of an offshore drilling operation, theoperation including a riser pipe and choke/kill lines attached thereto.

FIG. 2 is a close-up view of the riser pipe and the choke/kill lines.

FIG. 3 is a closer-up view of a male/female connection between conduitsforming a choke or kill line, and a seal sealing the interfacetherebetween.

FIG. 4A is an even closer view of the seal, the seal being shown in aninstalled interfacing condition between the two interfacing surfaces ofthe male/female parts.

FIG. 4B is a plan view of the seal in a pre-installation condition.

FIGS. 4C-4E are similar to FIG. 4B, except that the seal has beenmodified to include a hard heel and/or an internal expander.

FIG. 5A is a close-up view of another form of the seal, the seal beingshown in an installed interfacing condition between the interfacingsurfaces of the male/female parts.

FIG. 5B is a plan view of the seal of FIG. 5A in a pre-installationcondition.

FIGS. 5C-5E are similar to FIG. 5B, except that the seal has beenmodified to include a hard heel and/or an internal expander.

FIG. 6 is a partially-plan-partially-sectional view showing apiston-cylinder assembly wherein the seal is positioned in a groove inthe cylinder head to seal its reciprocating interface with the rod.

FIG. 7 is a partially-plan-partially-sectional view showing apiston-cylinder assembly wherein the seal is positioned in a groove inthe piston to seal its reciprocating interface with the cylinder.

DETAILED DESCRIPTION

Turning now to the drawings, and initially to FIG. 1, an offshoredrilling operation 10 is schematically shown. In this operation 10, adrillstring 12 extends from the rig 14 into a wellbore whereat it drillsdeeper and deeper into the sea floor. The drillstring 12 extends througha riser 16 which reaches from the rig platform to the wellhead, usuallywith a subsea blowout prevention (BOP) stack 18 between it and the oceanfloor. During drilling, mud removed from the wellbore is drained to thesurface through the riser 16, and well production fluid is transferredto the rig through choke lines 20. To stop a well flow, high density mudcan be pumped from rig tanks into the wellbore by kill lines 22 whichextend from the platform to the seafloor.

Turning now to FIG. 2, a portion of the riser 16 and the choke/killlines 20/22 are illustrated in more detail. As shown, the riser 16comprises successive riser pipes 24-26, and the choke line 20 and thekill line 22 each comprise successive conduits 28-30. The first conduit28 (or first part) has a female coupling member 32 and the secondconduit 30 (or second part) has male coupling member 34. Although thechoke line 20 and the kill line 22 are shown in the illustratedembodiment as being attached to the riser 16 (as is a common practice inoffshore drilling), they could instead be independently raised/loweredfrom rig. Also, the first part 28 and the second part 30 could insteadbe part of an auxiliary fluid line used, for example, for equipmentcontrol or logging purposes. Additionally or alternatively, the riserpipes 24-26 could themselves constitute the first/second parts 28/30.

As is shown more clearly in FIG. 3, the female coupling member 32 of thefirst conduit 28 has a cylindrical interacting surface 36 which is aradially inner surface and the male coupling member 34 of the secondconduit 30 has a cylindrical interfacing surface 38 which is a radiallyouter surface. The first conduit 28 and the second conduit 30 interact(e.g., connect) by relative linear movement between the respectiveinteracting surfaces 36 and 38, and the interacting surfaces 36/38interface with each other during such interaction. The female couplingmember 32 includes a groove 40 which extends radially outward from itsinteracting surface 36 and a seal 50 is positioned within this groove40.

The interfacing surfaces 36 and 38, the groove 40, and the seal 50 areshown even more clearly in FIG. 4A. The groove 40, which extends aroundthe circumference of the interacting surface 36, has two axial sides 52,a radial root side 54 spanning the root-adjacent edges of the axialsides 52, and an open radial side spanning the interface-adjacent edgesof the axial sides 52. The seal 50, which likewise extends around thecircumference of the interacting surface, comprises two axial faces 62,a root-adjacent radial face 64, and an interface-adjacent radial face66.

In FIG. 4A, the seal 50 is shown in an installed interfacing conditionand thus has a corresponding installed interfacing shape. In FIG. 4B,the seal 50 is shown in a pre-installation condition and has acorresponding pre-installation shape. The seal 50 will be an installedpre-interfacing condition after it is installed in the groove 40 butprior to interfacing with the interacting surface 38 of the second part30.

When the seal 50 is in its pre-installation shape (FIG. 4B), the axialseal faces 62 each have an axially concave profile and the root-adjacentseal face 64 has a radially concave profile. When the seal 50 is in itsinstalled interfacing shape (FIG. 4A), the interacting surface 36 of thesecond part 30 compresses the seal 50 direction. This results in theseal's root-adjacent face 64 assuming a flat profile flush against thegroove's root side 54. A substantial portion of the face 64 will contacta substantial portion of the groove side 54, though the corner regionsof the seal 50 may not contact the groove side 54.

The radial compression also causes each of the axial seal faces 62 toassume a more pronounced concave profile forming a fluid cavity 68. Whenthe fluid cavities 68 are filled with fluid, they push the seal face 64towards the groove's root side 54 and push the seal face 66 toward theinteracting surface 38 of the second part 30. Also, root-adjacentregions of the axial seal faces 62 will be urged against root-adjacentregions of the axial groove sides 52. Thus, contact (bearing) pressureis applied in at least four primary points: against the groove's rootside 54, against the interacting surface 38 of the second part 30, andagainst the root-adjacent regions of each of the groove's axial sides54. Such multi-point sealing allows bridging of surface imperfectionsallowing the seal 50 to be used in a groove that has deteriorated overservice/time.

In the illustrated embodiment, the seal's interface-adjacent face 66does not span the distance of the groove's open side 56 when in the seal50 is in the installed interfacing shape. The subsequent gaps from afluid passageway to the cavities 68. The seal 50 can be designed forabout 10% to 20% radial squeeze and about 5% to 15% free groove space,as such a combination may generate sufficient potential rebound energyfor effective sealing with many materials.

The seal 50 can be dimensioned so that, in the pre-interfacing installedcondition, its is somewhat axially compressed (e.g., 5%) within thegroove 40 and/or it is placed under hoop compression. Such a design canfacilitate holding the seal 50 during transportation and handling. Itmay also provide enough contact pressure at multiple sealing points toprevent moisture and possible corrosion of the groove 40 during storage.Additionally, rebound of the seal 50 from its installed interfacingshape to its installed-but-not-interfacing shape can be such that sealfaces 62 wipe or squeegee the groove sides 52 thereby preventingmoisture (e.g., seawater) from becoming trapped within the groove 40.

As shown in FIGS. 4C-4E, the seal 50 can be equipped with hard heels 70(FIG. 4C, FIG. 4E) and/or an internal expander 72 (FIG. 4D, FIG. 4E) toenhance seal performance. The heels 70 can serve as a backup foradditional pressure containment and/or increase extrusion resistance.The expander 72 can help maximize radially squeeze and/or optimizereactive rebound.

Referring now to FIGS. 5A-5E, another form of the seal 50 is shown. Inthis seal, the concave profile of the root-adjacent seal face 64 issharper and more triangular when the seal 50 is in its pre-installationcondition (FIG. 5B). When the seal 50 is in the interfacing condition(FIG. 5A), this face has a flat profile flush against the groove's rootside 54, and tightly engages its corner regions (although a centerregion) may be left uncontacted. Also, the seal's interface-adjacentface 60 fully occupies the groove's open side 54. The seal 50 mayinclude a hard heel 70 (FIGS. 5C and 5E) and/or an internal expander 72(FIG. 5D and FIG. 5E).

The seal 50 may be conventionally molded, extruded and cut, or otherwiseformed of an elastomeric material which specifically may be selected forhigh temperature performance, flexibility, or otherwise forcompatibility with the fluid being handled. Suitable materials, whichmay be filled, for example, with glass or carbon, or which may beunfilled, include natural rubbers such as Hevea and thermoplastic, i.e.,melt-processible, or thermosetting, i.e., vulcanizable, syntheticrubbers such as fluoropolymer, chlorosulfonate, polybutadiene, butyl,neoprene, nitrile, polyisoprene, buna-N, copolymer rubbers such asethylene-propylene (EPR), ethylene-propylene-diene monomer (EPDM),nitrile-butadiene (NBR) and styrene-butadiene (SBR), or blends such asethylene or propylene-EPDM, EPR, or NBR. The term “synthetic rubbers”also should be understood to encompass materials which alternatively maybe classified broadly as thermoplastic or thermosetting elastomers suchas polyurethanes, silicones, fluorosilicones, styrene-isoprene-styrene(SIS), and styrene-butadiene-styrene (SBS), as well as other polymerswhich exhibit rubber-like properties such as plasticized nylons,polyolefins, polyesters, ethylene vinyl acetates, fluoropolymers, andpolyvinyl chloride. As used herein, the term “elastomeric” is ascribedits conventional meaning of exhibiting rubber-like properties ofcompliancy, resiliency or compression deflection, low compression set,flexibility, and an ability to recover after deformation, i.e., stressrelaxation. Non-elastomeric compounds that also may be possiblecandidates include graphite, peek, and a wide variety of other materialsincluding composites.

As was indicated above, the fluid assembly which incorporates the groove40 and the seal 50 may be a choke line 20, a kill line 22, riser 16 orany other fluid-conveying line in an offshore drilling operation or, forthat matter, any suitable fluid-conveying system. Moreover, the fluidassembly need not include a conventional fluid-conveying system and/or afluid connection in such a fluid-conveying system. The presentgroove/seal arrangement may find application in any fluid assemblywherein cylindrical surfaces interact by relative linear movementtherebetween and a fluid seal is required in the interface between theinteracting surfaces. For example, as shown in FIGS. 6 and 7, the fluidassembly incorporating the seal 50 and the seal 40 can comprisepiston-cylinder assembly. Specifically, as shown in FIG. 6, the firstpart 28 can comprise the cylinder head and the second part 30 cancomprises the rod. The interacting surface 36 of the first part 28 isthe radially inner surface forming the rod-receiving bore (with thegroove 40 extending radially outward therefrom) and the interactingsurface 38 of the second part 30 is the radially outer surface of therod. As shown in FIG. 7, the first part 28 can comprise the piston andthe second part 30 can comprise the cylinder, with the groove 40extending radially inward from the interacting surface 36 of the piston.

Although the fluid assembly and/or seal has been shown and describedwith respect to a certain embodiment or embodiments, it is obvious thatequivalent alterations and modifications will occur to others skilled inthe art upon the reading and understanding of this specification and theannexed drawings. In regard to the various functions performed by theabove described elements (e.g., components, assemblies, systems,devices, compositions, etc.), the terms (including a reference to a“means”) used to describe such elements are intended to correspond,unless otherwise indicated, to any element which performs the specifiedfunction of the described element (i.e., that is functionallyequivalent), even though not structurally equivalent to the disclosedstructure which performs the function. In addition, while a particularfeature may have been described above with respect to only one or moreof several illustrated embodiments, such feature may be combined withone or more other features of the other embodiments, as may be desiredand advantageous for any given or particular application.

1. A fluid assembly comprising a first part, a second part, and a sealpositioned within a groove in the first part; the first part having acylindrical interacting surface and the second part having a cylindricalinteracting surface, one of these interfacing surfaces being a radiallyinner surface of the part and the other of these interacting surfacesbeing a radially outer surface of the part; the first part and thesecond part interacting by relative linear movement therebetween, therespective interacting surfaces and the interacting surfaces interfacingwith each other during such interaction; the groove extending around thecircumference of the interacting surface of the first part, the groovehaving two axial sides extending radially outward/inward from theinteracting surface, and a root side spanning terminating edges of theaxial sides; the seal comprising two axial faces, a root-adjacent radialface, and an interface-adjacent radial face; the seal having apre-installation shape prior to installation into the groove, aninstalled pre-interfacing shape when installed in the groove but priorto the second part interfacing with the first part, and an interfacingshape when the second part interfaces with the first part; theroot-adjacent radial face having a radially concave profile when theseal is in its pre-installation shape and a flat profile flush againstthe groove root side when the seal is in its interfacing shape, the flatprofile applying surface contact pressure against the groove root side;and the axial faces each having a radially concave profile when the sealis in its pre-installation shape and a more pronounced radially concaveprofile when the seal is in its interfacing shape; the more pronouncedradially convex profiles forming cavities which, when filled with fluid,urge the root-adjacent seal face towards the groove root side and urgethe interface-adjacent seal face towards the interfacing surface of thesecond part.
 2. A fluid assembly as set forth in claim 1, wherein thecylindrical interacting surface of the first part is the radially innersurface and the groove extend radially outward therefrom.
 3. A fluidassembly as set forth in claim 1, wherein the cylindrical interfacingsurface of the first part is the radially outer surface and the grooveextends radially inward therefrom.
 4. A fluid assembly as set forth inclaim 1, wherein root-adjacent regions of the seal axial faces of theseal apply surface contact pressure against root-adjacent regions of thegroove axial sides.
 5. A fluid assembly as set forth in claim 1, whereinthe concave profile of the root-adjacent radial face, when the seal isthe relaxed pre-installation condition, is symmetrical relative to sealcircumference.
 6. A fluid assembly as set forth in claim 1, wherein theconcave profiles of the axial seal faces are symmetrical relative to theseal circumference.
 7. A fluid assembly as set forth in claim 1, whereinroot-adjacent regions of the seal axial faces are axially compressedwhen the seal is in its installed pre-interfacing condition.
 8. A fluidassembly as set forth in claim 1, wherein the seal further comprises ahard heel.
 9. A fluid assembly as set forth in claim 1, wherein the sealfurther comprises an internal expander.
 10. A fluid assembly as setforth in claim 1, wherein the seal is made from an elastomeric polymericmaterial.
 11. A fluid assembly as set forth in claim 10, wherein theelastomeric polymeric material is selected from the group consisting offilled or unfilled natural rubbers, synthetic rubbers, andfluoropolymers.
 12. A fluid assembly as set forth in claim 1, whereinthe first part comprises a first conduit having a female coupling memberand the second part comprises a second conduit having a male couplingmember, the conduits forming a fluid line when coupled together, andwherein the interfacing surface of the first part in a radially innersurface of the female coupling member and the groove extends radiallyoutward therefrom.
 13. A fluid assembly as set forth in claim 12,wherein the fluid line is a choke line or a kill line in an offshoredrilling system.
 14. A fluid assembly as set forth in claim 1, whereinthe first part comprises a cylinder head having a central bore and thesecond part comprises a rod extending through the central bore, andwherein the interfacing surface of the first part is the radially innersurface forming the central bore and the groove extends radially outwardtherefrom.
 15. A fluid assembly as set forth in claim 1, wherein thefirst part comprises a piston and the second part comprises a cylinderand wherein the interfacing surface of the first part is the radiallyouter surface of the piston and the groove extends radially inwardtherefrom.